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Infrared Spectra of Small Insertion and Methylidene Complexes in Reactions of Laser-Ablated Nickel Atoms with Halomethanes

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Infrared Spectra of Small Insertion and Methylidene Complexes in Reactions of Laser-Ablated Nickel Atoms with Halomethanes Organometallics XXXX, XXX, 000–000 A DOI: 10.1021/om900498m Infrared Spectra of Small Insertion and Methylidene Complexes in Reactions of Laser-Ablated Nickel Atoms with Halomethanes Han-Gook Cho,† Lester Andrews,*,‡ Bess Vlaisavljevich,§ and Laura Gagliardi§,^ †Department of Chemistry, University of Incheon, 177 Dohwa-dong, Nam-ku, Incheon, 402-749, South Korea, ‡Department of Chemistry, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904-4319, §Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431, and ^Department of Physical Chemistry, University of Geneva, 30, q. E. Ansermet, 1211 Geneve, Switzerland Received June 12, 2009 Nickel carbene complexes, CX2dNiX2, are prepared along with the insertion products, CX3-NiX, in reactions of laser-ablated Ni atoms with tetrahalomethanes. These reaction products are identified from matrix infrared spectra and density functional frequency calculations. In agreement with the previously studied Pt cases, the carbon-nickel bonds of the Ni carbene complexes are essentially double bonds with CASPT2-computed effective bond orders of 1.8-1.9. On the other hand, only insertion complexes are generated from dihalomethane and trihalomethane precursors. The nickel carbenes have staggered structures, and several insertion complexes containing C-Cl bonds reveal distinct bridged structures similar to those observed in the corresponding Fe products, which indicate effective coordination of Cl to the metal center. The unique F-bridged CH2F-NiCl structure is also observed. Introduction actinides with small alkanes and halomethanes via C-H(X) insertion following H(X) migration.5-9 These complexes High oxidation-state complexes, first introduced in the also show distinct structures, particularly due to agostic 1 1970s, are now considered an essential part of coordination interaction and dramatic photochemical reactions including chemistry and help to understand the nature of carbon-metal photoreversibility. Their small sizes make them ideal for 2 bonds. Their rich chemistry includes growing applications in high-level theoretical approaches and, therefore, are consid- numerous syntheses including metathesis, catalytic properties, ered as model systems for their much larger cousins. The 3 and C-H insertion. Their distinct structures and photoche- higher oxidation-state complexes, however, are expected to mical properties have also provided testing grounds for be less favored on going far right among the transition metals 4 theoretical applications. in the periodic table because the d-orbital becomes more Recently small high-oxidation-state complexes have been filled. reported from reactions of group 3-8 transition metals and More recently small Pt carbene complexes, along with the Publication Date (Web): September 9, 2009 | doi: 10.1021/om900498m insertion products, have been identified in reactions with *To whom correspondence should be addressed. E-mail: lsa@ 10 - Downloaded by UNIV DE GENEVA on September 9, 2009 | http://pubs.acs.org methane and halomethanes. The C Pt bond orders com- virginia.edu. (1) (a) Fischer, E. O.; Kreis, G.; Kreiter, C. G.; Muller,€ J.; Huttner, puted by density functional theory and natural bond order G.; Lorenz, H. Angew. Chem., Int. Ed. Engl. 1973, 12, 564. (b) Schrock, R. range from 1.41 to 1.70 as Cl is replaced by F since the R. J. Am. Chem. Soc. 1974, 96, 6796. more electronegative halogen evidently supports a stronger (2) (a) Herndon, J. W. Coord. Chem. Rev. 2009, 253, 1517. carbon-metal bond. The small Pt methylidenes have a (b) Herndon, J. W. Coord. Chem. Rev. 2009, 253, 86. (c) Herndon, J. W. - Coord. Chem. Rev. 2007, 251, 1158. (d) Herndon, J. W. Coord. Chem. Rev. substantial amount of double bond character from dπ pπ 2006, 250, 1889. (e) Herndon, J. W. Coord. Chem. Rev. 2005, 249, 999. bonding, and their C-Pt bonds are considerably shorter (f) Herndon, J. W. Coord. Chem. Rev. 2004, 248, 3, and earlier review articles in this series. (3) (a) Crabtree, R. H. Chem. Rev. 1995, 95, 987, and references (6) (a) Cho, H.-G.; Andrews, L. J. Phys. Chem. A 2007, 111, 2480. therein. (b) Wada, K.; Craig, B.; Pamplin, C. B.; Legzdins, P; Patrick, B. O.; (b) Cho, H.-G.; Andrews, L. Organometallics 2007, 26, 633. (Group 3). Tsyba, I.; Bau, R. J. Am. Chem. Soc. 2003, 125, 7035. (c) Ujaque, G.; (7) (a) Cho, H.-G.; Andrews, L. Organometallics 2007, 26, 4096. Cooper, A. C.; Maseras, F.; Eisenstein, O.; Caulton, K. G. J. Am. Chem. Soc. (b) Cho, H.-G.; Andrews, L. Inorg. Chem. 2008, 47, 1653. (Re). 1998, 120, 361. (8) (a) Cho, H.-G.; Lyon, J. T.; Andrews, L. Organometallics 2008, (4) Clot, E.; Eisenstein, O. In Computational Inorganic Chemistry; 27, 5241. (b) Cho, H.-G.; Andrews, L. Eur. J. Inorg. Chem. 2008, 2537. Kaltzoyannis, N., McGrady, J. E., Eds.; Structure and Bonding; Spring- (c) Cho, H.-G.; Andrews, L. Organometallics 2008, 27, 1786. (Group 8). er: Heidelberg, 2004; pp 1-36. Aubert, C.; Buisine, O.; Malacria, M. Chem. (9) (a) Andrews, L.; Cho, H.-G. J. Phys. Chem. A 2005, 109, 6796. Rev. 2002, 102, 813, and references therein. (b) Cho, H.-G.; Lyon, J. T.; Andrews, L. J. Phys. Chem. A 2008, 112, 6902. (5) (a) Andrews, L.; Cho, H.-G. Organometallics 2006, 25, 4040, and (c) Lyon, J. T.; Cho, H.-G.; Andrews, L. Eur. J. Inorg. Chem. 2008, 1047 references therein (review article, groups 4-6). (b) Lyon, J. T.; Cho, H.-G.; (Actinides). Andrews, L. Organometallics 2007, 26, 2519 (Ti, Zr, Hf þ CHX3,CX4). (10) (a) Cho, H.-G.; Andrews, L. J. Am. Chem. Soc. 2008, 130, 15836. (c) Lyon, J. T.; Cho, H.-G.; Andrews, L. Organometallics 2007, 26, 6373 (b) Cho, H.-G.; Andrews, L. J. Phys. Chem. A 2008, 112, 12293. (c) Cho, (Cr, Mo, W þ CHX3,CX4). H.-G.; Andrews, L. Organometallics, 2009, 28, 1358. (Pt). r XXXX American Chemical Society pubs.acs.org/Organometallics B Organometallics, Vol. XXX, No. XX, XXXX Cho et al. than those of typical Pt(II) carbene complexes, leading to a conclusion that the small Pt methylidene complexes have substantial Pt(IV) character.11 As a continuation of our investigation on the chemistry of small transition-metal high-oxidation-state complexes, we re- port reactions of Ni with halomethanes. In contrast to the case of Pt,10 which is considered as the most effective C-H insertion agent among group 10 metals,10,12 only tetrahalomethanes generate Ni methylidenes. Several insertion products have interesting structures, particularly due to intermolecular inter- action between X bonded to C and the metal center. Experimental and Computational Methods Laser-ablated nickel atoms were reacted with CCl4 (Fisher), 13 CCl4 (90% enriched, MSD Isotopes), CFCl3,CF2Cl2 (Dupont), CHCl3,CH2Cl2,CH2FCl, CH2F2 (Dupont), CDCl3, 13 CD2Cl2 (MSD Isotopes), CD2FCl, and CD2F2 (synthesized )in excess argon during condensation at 10 K using a closed-cycle refrigerator (Air Products Displex). These methods have been described in detail in previous publications.10,14 Reagent gas - mixtures were in the range 0.2 1.0% in argon. The Nd:YAG - -1 laser fundamental (1064 nm, 10 Hz repetition rate, 10 ns pulse Figure 1. Infrared spectra in the 1000 800 cm region for the width) was focused on a rotating metal target (Ni, 99.99%, reaction products of the laser-ablated nickel atom with CCl4 iso- Johnson Matthey) using 5-10 mJ/pulse. After initial reaction, topomers in excess argon at 10 K. (a) Ni and CCl4 (0.5% in argon) -1 λ infrared spectra were recorded at 0.5 cm resolution using a co-depositedfor1h.(b)As(a)aftervisible( > 420 nm) irradiation. Nicolet 550 spectrometer with a Hg-Cd-Te range B detector. (c) As (b) after ultraviolet (240-380 nm) irradiation. (d) As (c) after Then samples were irradiated for 20 min periods by a mercury arc full arc (λ > 220 nm) irradiation. (e) As (d) after annealing to 26 K. 13 street lamp (175 W) with the globe removed using a combination (f) Ni and CCl4 reagent (0.5% in argon) co-deposited for 1 h. (g-j) of optical filters or annealed to allow further reagent diffusion. As (f) spectra taken following the same irradiation and annealing To provide support for the assignment of new experimental sequence. i and m designate the product absorption groups, while - frequencies and to correlate with related works,5 10 density func- P and c stand for the precursor and common absorptions. tional theory (DFT) calculations were performed using the Gauss- ian 03 program system,15 the B3LYP and BPW91 density and the optimized geometry was confirmed by vibrational analysis. functionals,16,17 and the 6-311þþG(3df,3pd)basissetsforC,F,Cl, The vibrational frequencies were calculated analytically, and zero- and Ni atoms.18 Geometries were fully relaxed during optimization, point energy is included in the calculation of binding and reaction energies. Previous investigations have shown that DFT-calculated harmonic frequencies are usually slightly higher than observed (11) Prokopchuk, E. M.; Puddephatt, R. J. Organometallics 2003, 22, frequencies,5-10,19 and they provide useful predictions for infrared 563, and references therein. Pt(IV). spectra of new molecules. Natural bond orbital (NBO) analysis15,20 (12) (a) Carroll, J. J.; Weisshaar, J. C.; Siegbahn, P. E. M.; Wittborn, - C. A. M.; Blomberg, M. R. A. J. Phys. Chem. 1995, 99, 14388. (b) Low, J. was done to help understand the carbon nickel bonding in the J.; Goddard, W. A.III. Organometallics 1986, 5, 609. (c) Wang, X.; Andrews, carbenes, but the results were questionable, and the carbenes were L. J. Phys. Chem. A 2004, 108, 4838. (d) Cho, H.-G.; Andrews, L. J. Phys. examined using CASSCF/CASPT2 methods and triple-ζ (ANO- Chem. A 2004, 108, 6272. RCC-VTZP) basis sets.21,22 An active space of (6,6) was chosen for (13) Isotopic modifications synthesized: Andrews, L.; Willner, H.; the active orbitals involved in the C-M bond.
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